Base line: the imaginary line upon which all type
rests x-height: the main part of the lower case which
is equal to the height of the lowercase x Ascender: the part of the letter form of the lower
case which rises above the x-height as in b, d,
f, h, k or l Descender: the part of the letter g,
j, p, q and y
that extends below the baseline

Cap height: height of the capital letter. The ascenders
of some lowercase actually rises sometimes a little bit above
the cap height. Type size: refers to the overall depth of the typeface
and is measured from the top of the highest character to the foot
of the lowest.

Serif: a short stroke that projects from the ends
of the character. The serifs help to keep letters a certain distance
apart, they link letters together to form word which helps reading
and finally they help to differenciate individual letters. Stroke or stem: vertical or oblique part of a letter.
It can be more or less thick or thin.
Counter: An enclosed or partially enclosed portion of a type character
such as p, q or b